ABSTRACT The goal of this Fast-Track STTR project is to develop a Deterministic Lateral Displacement (DLD) microfluidic device that can enrich white blood cells (WBCs) from a typical leukapheresis unit in 1 hr, for use in manufacturing cancer cellular immunotherapy. Chimeric antigen receptor T cell (CAR-T) therapy has been recommended for FDA approval to treat relapsed or refractory pediatric and young adult patients with B-cell acute lymphoblastic leukemia. There is a critical need for cost-effective automated methods to improve the efficiency and yield of large-scale enrichment of WBCs for use in manufacturing CAR-T and other cellular therapies. GPB is a pioneer in developing novel DLD microchips to process blood cells for cell analysis (19,26). GPB now proposes to develop, evaluate and commercialize a compact device in which an entire leukapheresis unit (up to 5x1010 WBCs in up to 300 ml) can be processed in a ?Leuko-stack? of disposable single-use multi-channel DLD chips to produce in 1 hr a washed cell suspension that is enriched in WBCs and depleted of red blood cells (RBCs) and platelets (PLT). In Phase I, Aim 1 is to increase cell throughput through the current prototype chips by: 1) optimizing DLD chip design and operation to increase flow rate; 2) increasing throughput by stacking plastic chips and running them in parallel (?Leuko-stacks?); and 3) translating chip production to high-volume manufacturing material such as Cyclic Olefin Polymer (COP). Final Phase I milestones to proceed to Phase II are: 1) final chip design with a flow rate of at least 25 mL/hr via a single chip, at least 70% recovery of viable WBCs and immunophenotype- defined T-lymphocytes, and ability to process cells for 1 hr without clogging; 2) Leuko-stack of at least 6 chips run in parallel, with the same output as in #1; 3) combined increases in throughput via #1 and #2 sufficient to process a 300 ml leukapheresis unit in 1 hr; 4) confirmation that the chips can be produced from COP. In Phase II, Aim 2 is to build final prototype COP plastic chip-based microfluidic device capable of processing a leukapheresis sample at 300 mL/hr. Aim 3 is to test performance of prototypes from Aim 2 with leukapheresis aliquots and then full-size human leukapheresis samples. The final milestone of this project is to produce a set of commercial prototype Leuko-stacks that can process an entire 300-ml leukapheresis unit in 1 hr with at least 70% WBC and T-lymphocyte recovery, at least 90% depletion of RBCs, at least 80% depletion of PLTs, and at least 70% recovery of T-cell expansion capacity (as compared with the input samples) in significantly more than 50% of samples tested at 2 sites. The GPB Leuko-stack platform will preserve the advantages of DLD microfluidic cell processing over current methods, while massively increasing throughput rate and cell processing capacity, thus transitioning from analytic- to preparative-scale WBC enrichment for subsequent manufacture of CAR-T and other cell therapies.